Recently, the widespread use of hybrid cars, which can be driven by the energy of both gasoline and electricity, and devices requiring power supplies, such as uninterruptible power supplies, mobile communications devices, and portable electronic devices, has created an enormous need for improvements in the performance of rechargeable storage devices used therefor as power supplies. Specifically, there is a need for improved properties such as increased power, capacity, and cycle life.
To provide storage devices with such properties, research has been directed to the use of organic compounds as electrode active materials. Recently, organic compounds having a π-electron conjugated cloud have been suggested as novel active materials capable of absorbing and releasing lithium, which has the potential for high-speed charge and discharge (see, for example, Patent Documents 1 and 2). Also suggested is a lithium-dicarboxylate containing conjugated organic active material having an organic backbone composed of dilithium trans-muconate or dilithium terephthalate (see, for example, Non-Patent Document 1). This active material is characterized in that its organic backbone has a conjugated structure, which allows oxidation and reduction (absorption and release of lithium).
Also suggested are negative electrodes based on the conversion reaction of a metal oxide (e.g., MOx, where M is Fe, Co, Ni, Cu, Mn, or the like) such as manganese oxide or iron oxide (see, for example, Non-Patent Documents 2 to 4). These negative electrodes are charged and discharged by the reaction formula MOx+xe−+2xLi+→M+xLi2O.
[Patent Document 1] JP 2004-111374 A
[Patent Document 2] JP 2004-342605 A
[Non-Patent Document 1] Nature Material, Vol. 8, 120-125 (2009)
[Non-Patent Document 2] Nature Material, Vol. 5, 567-573 (2006)
[Non-Patent Document 3] J. Power Sources., 196, 3346-3349(2011)
[Non-Patent Document 4] Electrochm. Commu., 8, 383-388 (2006)